The long term objective of this research is to achieve successful gene therapy of human diseases of the hematopoietic system, specifically of the beta thalassemias and sickle cell anemia. Our specific aims are: to design new retroviral vectors for efficient selection of infected totipotent hematopoietic stem cells so as to achieve 100 percent long-term reconstitution of transplanted animals and complete elimination of non- infected cells; to infect human and murine totipotent hematopoietic stem cells from normal and beta-thalassemic subjects with optimized retroviral vectors for transferring human beta globin gene and Locus Control Region derivatives and to test their in vivo properties; and to transfer a globin gene by retroviral vectors for gene therapy of sickle cell disease. These pre-clinical studies are designed to provide the scientific and technologic basis for subsequent clinical studies of gene therapy of these hematologic disorders. This proposal represents a collaboration between Irving M. London, Philippe LeBoulch and Dorothy Tuan of the Harvard-MIT Division of Health Sciences and Technology of MIT, Connie Eaves and R. Keith Humphries of the Terry Fox Laboratories of the British Columbia Cancer Agency, and Yves Beuzard of the University of Paris XII.